The present invention is generally related to permanent magnet linear brakes and is more particularly directed to an eddy current brake and magnet system for providing adjustable braking for movable cars, for example, rail support cars, go cars, elevator cars, conveyer car, roller coaster cars among other.
Heretofore, eddy current braking system for providing deceleration of moving apparatus have utilized physically fixed magnets which provided no opportunity to adjust braking before or during passage of a diamagnetic member past a linear array of permanent magnets.
Accordingly, such prior art systems, when installed for decelerating a plurality of cars on a track, can not accommodate for variations in car weight and size.
The present invention provides for a unique permanent array arrangement and apparatus for adjusting braking force before and/or during passage of a car past a selected point.
An eddy current brake in accordance with the present invention generally includes a diamagnetic or non-magnetic member, a first support wall and a separate second support wall disposed in a spaced apart relationship with the first support wall for enabling the member to pass therebetween.
A first linear array of permanent magnets is disposed on the first wall on the side facing the second wall and a second linear array of permanent magnets is disposed on the second wall on the side facing the first wall. The first and second arrays are parallel with one another and spaced apart from one another for allowing passage of the member therebetween and causing eddy current to be induced in the member which results in the braking force between the magnets and the member. No magnetic connection, such as a yoke, is required between the walls or the arrays of permanent magnets. This feature enables adjustability of the distance between the member and the magnet arrays.
In accordance with the present invention, apparatus is provided for moving a least one of the first and second walls in order to control eddy current induced in the member during the passage of the member therepast in order to adjust braking force between the magnets and the member. In one embodiment of the present invention, the apparatus includes means for moving at least one of the first and second walls in a direction perpendicular to the member, and in another embodiment of the present invention, the apparatus includes means for moving at least one of the first and second walls in a direction parallel to the member.
Thus, it can be seen that the apparatus in accordance with the present: invention provides for changing the spaced apart relationship between the first and second walls in order to control eddy current induced in the member during passage and adjust a braking force between the magnets and member.
Accordingly, the amount of deceleration provided to a given car may be adjusted in accordance with the present invention. In addition, cars of various sizes and weights may be utilized and the eddy current magnetic brake in accordance with the present invention adjusted to provide the proper, or desired, deceleration. In one embodiment to the present invention, apparatus is provided for adjusting the eddy current induced in the member, and the braking force, as a function of velocity of the member between the arrays. Thus, cars having various velocities upon passing the brake, can be decelerated to a more uniform velocity exiting the brake in accordance with the present invention.
In this embodiment of the brake, the apparatus for adjusting eddy current includes a linkage mounting at least one of the first and second walls to a fixed foundation for enabling movement of the member therepast to change a distance between at least one of the first and second walls and the member. More particularly, the linkage may provide for changing a spaced apart relationship between the first and second walls.
An embodiment of the present invention includes linkage for enabling movement of the member to change a transverse relationship between at least one of the first and second walls of the member and another embodiment provides linkage for enabling movement of the member to change a parallel relationship between the first and second walls and the member.
Magnetic coupling and inducement of eddy current is effective through a linear array of permanent magnets which includes a channel and plurality of magnets disposed therein. The magnets may be arranged within the channel in two adjacent rows with each magnet in each row being arranged with a magnetic field at a 90xc2x0 angle to adjacent magnets in each row along the channel. Each magnet in each row is also arranged with a magnetic field at an angle to another adjacent magnet in the adjacent row.